The human axilla (i.e., underarm) is a region of the human body that contains a high density of apocrine glands that produce and secrete sweat, as occurs during increased physical activity or exposure to heat. Also, it has been known for many years that sweat (or perspiration) per se contains odorless precursors which, when acted upon by the axillary bacteria, produce sugars, sugar amines, amino acids, and short chain carboxylic acids (SCCAs), of which some are degraded further to products that include odorants that are associated to a major extent with axillary odor (Zeng et al, 1991; Jackman, 1982).
The axillary microbiome in humans includes a variety of microorganisms, of which staphylococci, corynebacteria and propionibacteria are among the most prominent (Starkemann et al., 2005, Troccaz et al., 2004, Jackman, 1982). A study of 229 subjects by Leyden et al. (1981) established that axillary odor typically includes a strong pungent and a weak secondary odor, that is acidic and generally of lesser intensity. Leyden et al. further found that the primary axillary bacteria responsible for the strong pungent odor were corynebacteria. More recently, Emter et al. (2008) narrowed this finding to specific species among the corynebacteria. Leyden et al. (2002) demonstrated that staphylococci and other axillary bacteria also contribute to axillary odor. The contributions of these other (non-corynebacteria) bacteria to the odor bouquet are products that tend to be more acidic and less offensive in nature. What was not known was whether and/or how these two major odor streams might be related and if and how they could both be inhibited simultaneously. Such interaction and balancing are central to manipulating and modifying microfloras found in the oral cavity (Kleinberg et al., 2002), and possibly also in the vagina and large intestine. Such modification at these sites provide a more healthy condition, which may be termed dysbiotic to eubiotic microflora transformation.